Seven strains of porcine rotavirus, four of which (83/17F, 84/52F, 84/106F, 84/158F) had been isolated from diarrheic piglets in herds located in three regions (Lombardia, Veneto, Emilia) of Northern Italy, and the remaining three (SW 20/21, OSU, S80) obtained from the U.K., USA and Japan, respectively, were compared. The study included reciprocal serum neutralization tests as well as genomic RNA electrophoresis. The Italian isolates together with the U.K. (SW 20/21) and the USA (OSU) strains proved to belong to the same serological group, whereas the Japan (S80) strain appeared to be serologically distinct from the others. The gene segments of the viruses under study had identical or closely similar electrophoresis mobilities, with the only exception of S80 strain the genome profile of which was quite different from the other porcine rotavirus strains.